This invention relates generally to safety devices and, more particularly, to a driver sleep alarm for use in a vehicle which detects the condition of sleepiness or inattentive driving and alerts the driver thereof.
The reality of drivers becoming increasingly drowsy or even falling asleep while driving is a grave problem which carries well-publicized consequences. Even a momentary lapse in mental alertness and attentiveness often leads to the long-lasting disability or even death of the drowsy driver or to others. In addition, the grisly statistics of vehicular accidents resulting from drowsy drivers or drivers lacking adequate alertness due to drug or alcohol consumption do not reflect the mental anguish and sorrow suffered by the family and friends of persons needlessly injured or killed.
Many devices have been proposed in the art for alerting drivers of the condition of drowsiness. Many of these devices may be categorized as pressure responsive or grip-sensitive devices. Maintaining sufficient pressure on a steering wheel or other grip-sensitive structure for long periods of time, however, may lead to even further driver fatigue. In addition, implementation of pressure sensing transducers is complex and expensive, especially those which are adaptable to the pressure exerted by different drivers of a single vehicle.
Other systems, such as the alarm disclosed in U.S. Pat. No. 4,259,665, utilize a pair of conductive plates spaced apart about a steering wheel between which a current is communicated through the hand of the driver when placed in contact therewith. It has been found, however, that such a system is prone to electrical shorting from condensation on the steering wheel. Another problem is dry contact resistance wherein current is not delivered between the plates because a person's skin is very dry or the driver is wearing gloves. Still another problem with conductive systems is that the plates may become soiled and thus unable to consistently deliver current therebetween.
Another category of sleep alarms includes optical devices which must be worn about a driver's head or neck. These devices also contribute to driver fatigue as the driver holds his head rigidly so as to avoid inadvertently tripping the alarm. Other optical systems are mounted on the steering wheel itself and use optical beam deflection to monitor finger placement. These systems, however, require a protrusion on the back of the steering wheel for the light beam-shaping lens and require a driver's fingers to extend through the protrusions in an uncomfortable and unfamiliar manner.
Many sleep alarms from each of the above described categories include manual disabling switches whereby a driver may completely deactivate the device. Unfortunately, the complexity or disadvantages of these system often leads to such deactivation and non-use by drivers.
Therefore, it is desirable to have a driver sleep alarm which overcomes the above described disadvantages by sensing the position of a driver's fingertips on, or in close proximity to, a steering wheel without requiring any level of grip pressure, circuit formation, or optical sensing. Further, it is desirable to have a driver sleep alarm which operates effectively even when a driver is wearing gloves. In addition, it is desirable to have a driver sleep alarm which is not affected by humidity, condensation, light, or other environmental conditions. Finally, it is desirable to have a driver sleep alarm which may only be temporarily disabled by a driver.